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Published: October 25, 2023

Radiant Cooling Technology – A Sustainable Building Solution

In regions with tropical climates, a building's air conditioning and ventilation can be responsible for over 50% of its total energy usage. As the demand for cooling continues to climb—spurred by economic growth in developing nations and intensified by climate change—it's essential we pivot to more eco-friendly and energy-efficient cooling methods. One such solution that stands out is Radiant Cooling Technology.

This advanced method not only substantially cuts energy consumption but also enhances indoor air quality, ensuring a more comfortable environment for occupants.

Understanding Radiant Cooling System

Radiant cooling operates primarily on principles of radiation and convection heat transfer. Here's a simplified breakdown (See Fig. 1 for reference):

  1. Sensible Cooling: Chilled to about 14°C, water circulates through the system. After absorbing heat from the environment, the warmer return water is then sent back to the chiller at a temperature of around 19°C.
  2. Humidity and Ventilation: Fresh, dehumidified air is introduced to the area at roughly 12°C to regulate humidity levels and ensure proper ventilation.
  3. Efficient Cooling: The surfaces, usually ceilings, through which the chilled water flows, are kept at a temperature of 18-19°C. This direct cooling mechanism efficiently cools the room. Interestingly, about half of the heat transfer is radiative, while the other half is convective for these cooled surfaces.

Essential components of Radiant Cooling System

1. PEXa Pipes: Specialized PEXa pipes are created from a high-grade plastic raw material, HD polyethylene. Manufacturers of these pipes often claim a lifespan of 100 years, making them optimal for systems meant to be embedded and remain in place for extended periods. These pipes serve as the radiant surface and can be strategically concealed within various parts of a building (Fig. 2).

Depending on their placement, the radiant cooling system can take various forms: (a) radiant slab cooling - pipes embedded inside a slab during construction (Fig. 3); (b) radiant floor cooling - pipes embedded inside floor screed (Fig. 4); (c) radiant ceiling cooling - pipes embedded inside the false ceiling.

2. Centralized Radiant Cooling Plant: This plant is the heart of the radiant cooling system. It typically features, (1) a medium-temperature chiller circuit that supplies chilled water at 14°C to the radiant cooling surface and (2) a separate low-temperature chiller circuit supplying chilled water at 6.6°C for a dehumidification coil inside the treated fresh air unit so that the dehumidified ventilation air can be supplied to the zone below 12°C. 

3. Cold/Chilled Water Source: Radiant systems can harness chilled water from a variety of sources. Some of the prevalent methods include:

  • District Cooling Plant: A centralized facility that produces chilled water to be distributed across multiple buildings or sites.
  • Sea Water Air Conditioning (SWAC): Utilizes cold seawater sourced from depths of around 200m in the ocean.
  • Cooling Towers: These are especially useful in dry and moderate climates.
  • Groundwater Wells: Only when authorized by governing bodies.
  • Geothermal Piping Loops: Taps into the earth's consistent underground temperatures for cooling.
  • Deep Lake Water Source: A method similar to SWAC but using lake water.
  • Night Sky Cooling: An innovative approach where roof surfaces are used to radiate heat to the cooler night sky.

The Pros and Cons of Radiant Cooling Systems

1. Benefits of Radiant Cooling Systems:

    Energy efficiency-

  • Water's inherent capacity to absorb heat—approximately 3,500 times more than an equivalent volume of air—means significantly less energy is expended transporting chilled water than air in a building for the same cooling effect. This results in up to 80% energy savings on fan power. Radiant systems, using water temperatures of 14-15°C, can utilize up to 60% of a chiller's capacity, leading to over 25% savings on chiller energy. Cumulatively, this can reduce a building's total energy consumption by up to 50%.

     Enhanced Indoor Air Quality-

  • Operative Temperature: Radiant systems effectively manage surface temperatures, ensuring optimal thermal comfort. In contrast, conventional air systems often fall short of maintaining desired radiant temperatures.
  • Stable Temperatures: Radiant cooling maintains a consistent surface temperature, usually between 16-18°C, providing a steadier room temperature than traditional air systems.
  • Efficient Airflow: Requiring only minimal airflow for ventilation, radiant systems avoid the extensive air handling of traditional methods, ensuring optimum air velocity in occupied spaces.
  • Noise Reduction: Radiant systems eliminate the need for indoor air recirculation units, resulting in quieter interiors with noise levels below NC 25.
  • Dedicated Ventilation: With its primary focus on ventilation, the radiant system introduces fresh air through a specialized unit, preventing the mixing of return and fresh air, a common problem in conventional setups.

2. Challenges of Radiant Cooling Systems:

  • Resistance to Adaptation: Many professionals in the building industry, including architects and contractors, may be hesitant to adopt this technology due to the increased time and effort required in the design phase compared to traditional systems.
  • Aesthetic Considerations: For certain unique or non-traditional interior designs, integrating radiant cooling systems while maintaining desired aesthetics might pose challenges.
  • Initial Costs: Radiant cooling systems, especially those that use false ceilings, can be 10-15% more expensive initially than conventional cooling methods.
  • Complex Implementation: Implementing a radiant cooling system requires more meticulous coordination and planning than traditional systems.
  • Training: The operation staff will need additional training in the proper commissioning and management of a radiant cooling system.

The increasing number of installations, with over 60 in India alone, underscores the system's potential. It's not merely a novelty but a proven technology gaining traction in modern building designs. One notable example of its application is at the Tulah Wellness Centre in Calicut, Kerala, India.

Contact

Renew Consulting Engineers (Pvt) Ltd

No. 302, First floor, HRBR layout,

1st block, Kalyan Nagar, Bengaluru – 560043, Karnataka, India

www.renewconsulting.in

Mr. Jabish Joy (jabish.joy@renewconsulting.in § +91 7849005002)

Mr. Nandish P (nandish.p@reneAwconsulting.in § +91 9986677717)

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